Hermetically sealed miniature relay



Oct. 26, 1965 G. E. PIHL 3, ,53

HERMETIGALLY SEALED MINIATURE RELAY Filed July 24. 1962 INVENTOR.

GEORGE E. PIHL BY F I G. 5 wawmw ATTORNEYS United States Patent 3,214,534 HERMETICALLY SEALED MINIATURE RELAY George E. Pihl, Abington, Mass., assignor to Miniature Electronic Components C0rp., Holbrook, Mass, a corporation of Massachusetts Filed July 24, 1962, Ser. No. 212,103 Claims. (Cl. ZOO-87) This invention relates in general to electrical relays and more particularly to a miniature relay capable of withstanding extremely high acceleration.

The physical size of components in general and relays in particular has become an increasingly important design parameter for many electrical and electronic circuits. This emphasis results both from the complexity of many circuits, such as radar and computer circuits which involve thousands of components, and from volume and weight limitations imposed upon airborne instrumentation. In the former case, the individual electrical components must be miniaturized in order to provide that the finished assembly has a reasonable size while in the case of the airborne instrumentation, size and weight must be completely minimized in order to provide for maximum efiiciency of the flight. This is particularly true with reference to missile and satellite instrumentation where space requirements are even more stringent than in other more conventional airborne vehicles. Another requirement imposed upon electronic components to be included both in missiles and other weaponry is the ability to withstand extremely high acceleration and deceleration forces. Under these circumstances, an electronic component may be required to operate under extremely high forces.

It is, therefore, a primary object of the present invention to provide a miniaturized relay capable of withstanding extreme acceleration and having predictable and reliable switching characteristics.

Another object of the present invention is to provide a miniaturized relay which can be manufactured efiiciently and economically and in which both the pull-in and dropout characteristics may be adjusted after assembly.

Still another object of the present invention is to provide an efficient miniaturized relay which may be hermetically sealed after adjustment of its pull-in and drop-out characteristics.

A further object is to provide a miniature relay where its contacts will remain closed under extremely high G forces yet will open or close in response to relatively small current changes.

Broadly speaking, the present invention provides a miniaturized, hermetically sealed relay comprising discrete subassemblies which facilitate manufacture, final assembly, testing, and adjustment. The relay is designed to serve as an electrically operated single pole, double throw switch. External connections for each of the stationary contacts as well as the movable switching contact are provided. The movable switching contact is closed to one stationary contact upon the application of a suitable energizing current and is opened from this contact and closed to the other stationary contact when the energizing current falls below a preselected level. The modular construction of the relay is such that the pull-in and dropout characteristics may be adjusted after assembly, thus providing for precision setting of these characteristics. Moreover, hermetic sealing of the unit may be delayed until after all adjustments have been completed. What is even more significant about the modular construction is that it makes possible a relay whose final dimensions are a cylinder length of /2 inch and a cylinder diameter of inch.

Other objects and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a relay constructed in accordance with the principles of this invention;

FIG. 2 is a longitudinal sectional view of the same relay on an enlarged scale, with a portion of the header assembly thereof shown as in a full side view; and portions of two of the terminal leads omitted for clarity;

FIG. 3 is a cross-sectional view of the lower portion of the same relay taken along the line 33 of FIG. 1; and

FIG. 4 is a fragmentary longitudinal sectional view similar to FIG. 2 but with the relay rotated and one of the terminal leads omitted fully for clarity.

As shown in FIG. 1, the fully assembled relay is seen to have a cylindrical outer casing and a header identified generally at 2 and 4 respectively. The header includes five terminal leads 8, 10, 12, 14, and 16 through which the relay may be energized and connections made to its contacts. 7

Reference is now had to FIGS. 2, 3, and 4 for details of the magnetic subassembly of the relay. The magnetic flux for operation of the relay is generated by a coil of fine insulated magnet wire 18 on a hollow bobbin 20 formed of a suitable dielectric plastic material. Polyfiuoroethylene plastics such as those sold under the trademarks Kel-F and Teflon are suitable for this purpose. The ends of the wire terminate on separate electrically conductive segments 22 and 23 which are formed by photo-etching a copper laminated disc 24 which is fastened to the end of bobbin 20. The disc 24 is formed of an electrically insulating material, such as epoxy resin reinforced with fiberglass, and each of the conductive segments 22 and 23 are electrically insulated from one another. The ends of the wire are connected to segments 22 and 23 through suitable holes formed in disc 24. After the coil of wire 18 has been wound on the bobbin, it is covered by a layer of insulating material 25, such as a plastic tape. The outer casing 2 is fabricated from a magnetic material such as Norway iron and has the form of a hollow cylinder open at one end having a wall 26 with a tapped central opening 28 at the opposite end. The completed coil assembly comprising the bob bin 20 and the coil of wire 18 covered with the insulating material 25 is inserted into the hollow cylindrical casing 2 and is fastened to it by cement applied to the inside surface of the casing at 29. A hollow core element 31 completes the magnetic subassembly. Core element 31 is formed of the same material as the casing 2 and is inserted into the hollow body of the bobbin 20. It is provided with a threaded section 32 which mates with the internal threads of the central hole 28 in the casing 2. The exterior diameter of core element 31 is only slightly smaller than the internal diameter of the hollow body of the bobbin, thereby providing that the core element will be rotatable and also movable longitudinally relative to the bobbin, but not movable laterally.

The header assembly 4 fits into the open end of the casing. It comprises a header ring 35 formed of magnetic material such as low carbon steel and supporting a glass insert 36 which is molded around and supports leads 8, 10, 12, 14, and 16. This header ring 35 is soldered to the casing 2 during final assembly. A support block 37 formed of magnetic material such as Norway iron is welded to the inner end face of the header ring. An armature 38, again formed of magnetic material such as low carbon steel, is hinged to the block 37 by means of a small diameter wire 39 preferably made of iron, although copper also may be used. The wire 39 is bent in the form of a U and passed from underneath through two holes in the support block 37 and flattened into a groove in the bottom of the support block 37 before this block is welded to the header ring 35. The ends of the wire hinge 39 are then passed through two holes in the armature 38 and bent over to lie in a groove 40 formed in the armature. A small amount of play is intentionally provided between the armature and the hinge for a purpose described hereinafter. Since the casing 2, the header ring 35, the support block 37, the armature 38, and the core element 31 are all formed of magnetic material, on energization of the coil, they provide a magnetic circuit with a force of magnetic attraction appearing across the air gap between the armature 38 and the end of the core element 31 in such a way as to move the armature upward.

Gold alloy wire contacts 46 and 47 are welded to header wires 10 and 12, respectively. These contacts are in parallel spaced relation to each other, disposed at right angles to the center line of armature 38. Coil springs 49 and 50 are mounted on header wires 8 and 14 and contact segments 22 and 23 respectively. At this point, it is to be observed that the top ends of the header Wires 8 and 14 are offset outwardly away from the armature as indicated at 51 in FIG. 4. This is done for a variety of reasons. First of all, it is done to equalize the gap between them and the armature on the one hand and the casing on the other hand, so as to achieve better insulation against voltage breakdown. Secondly, it is done to hold the bottom ends of the springs spaced from the body of the header so as to prevent them from touching the header ring 35. A third reason is to provide a positive secure contact between header wires 8 and 14 and coil springs 49 and 50 respectively. The bend in the leads holds the springs compressed against segments 22 and 23 at all times regardless of vibration or G force. Header Wires 10, 12, and 16 are bent in a similar manner for maximum insulation. The remaining header wire 16 is connected by a flexible (preferably insulated) Wire 52 to a movable, slightly flexible contact 54 which has one end attached to the armature 38 by means of an insulator 56. The movable contact extends radially across the inside of the casing between and at a right angle to stationary contacts 46 and 47.

As indicated previously, the armature is moved upward by the magnetic force when the coil is energized. The action of the magnetic force upon the armature 38 is opposed by the action of a coil spring assembly. The latter comprises a compression spring and a screw plug 62. Spring 60 is inserted within the core element 31 and is held against the armature by plug 62 which mates with internal threads at the remote end of core element 31. The tension of the spring 60 and its resultant force upon the armature 38 may be varied by adjusting the position of screw plug 62 in core element 31. The spring 60 acts through the armature 38 to hold movable contact 54 against contact 47 when the coil is de-energized. Upon energization, the resultant magnetic field will cause the armature to pivot so that its contact 54 will open relative to contact 47 and close immediately on contact 46. The pull-in and drop-out characteristics of this relay may be adjusted (1) by adjusting the position of screw plug 62 in core element 31, thereby varying the spring tension upon the armature 38, and (2) by varying the position of core element 31 in the casing 2, thereby varying the gap between the armature 3S and the end of the core element. After the pull-in and drop-out values have been adjusted, the entire unit may be sealed off by a mass of solder 66 placed in the central hole 28 of the end wall of the casing.

It is to be noted that the contact 54 is only slightly flexible and has sufiicient stitfness to prevent armature 38 from engaging core element 31 when the coil is energized with the prescribed voltage, whereby to leave a gap, hereinafter termed main gap, between the armature and the core element. This main gap is essential to avoid a sharp decrease in reluctance which in turn would lower the drop-out current to an unsatisfactory value.

In this connection, it is to be observed that one of the essential features of the illustrated construction lies in the magnetic properties of the hinge arrangement holding the armature 38 to the block 37. When the coil is deenergized, the armature 38 is in intimate contact with the support block 37 as a result of the pressure of the spring 68. This minimizes the magnetic leakage at this point and hence a minimum pull-in current is required. However, when the coil 18 is energized so that the armature 38 is pulled upward, a small auxiliary gap is provided between the armature 38 and the block 37 as a result of the play between the wire hinge 39 and the armature. Notwithstanding the connection alforded by ironwire 39, this auxiliary gap reduces the flux in the main gap between the armature 38 and the core 31, and thus enables the drop-out current to occur at a higher value. The path between the armature and block 37 afforded by the iron wire 39 has great reluctance due to the small diameter of the wire; therefore, it does not oflset the affect on the flux produced by the auxiliary gap.

The compression spring 60 acting against the armature is one of the primary factors which makes it possible to construct a relay capable of withstanding a pressure force of 40 GS for either position of the movable contact. If the relay is to operate with a force of 40 Gs applied to it when the movable contact is closed on contact 47, the armature must be held down by a loading force of the same magnitude when the relay is at rest and deenergized. This loading is achieved by spring 60 by exerting a force on the armature equal to approximately 40 times the effective mass of the armature and its contact. Because of this loading, the magnetic attractive force exerted on the armature while the coil is energized must be at least GS to counteract the affect of an external force of 40 GS. Otherwise, the movable contact will not remain seated firmly on contact 46 but may chatter or even be held open. The number of turns of the coil is sufliciently large to generate a magnetic field of the desired intensity. Due to the inherent resiliency of the slightly flexible contact, it will allow slight motion of the armature under vibratory conditions without momentary contact opening in either the energized or deenergized condition.

Typical values at room temperature for the coil of a miniature 28-volt D.C. relay embodying the above-described construction are as follows:

Coil

Nominal resistance 2800 Max. continuous v v 30 Max. intermittent v. v 32 Max. pull-in v. v 20 Min. drop-out v .v 8 Max. continuous I ma 10.5 Max. intermittent I ma 11.5 Max. pull-in I ma- 7 Min. drop-out I ma 3 Having described the invention, various modifications and improvements will now occur to those skilled in the art. Therefore, the invention disclosed herein should be construed as limited only by the spirit and scope of the appended claims.

I claim:

1. A relay comprising first and second fixed contacts, an armature having a third contact, means pivotally mounting said armature for movement between a first position wherein said third contact engages said first fixed contact and a second position wherein said third contact engages said second contact, a coil for generating a magnetic field so that said armature can be pivoted magnetically to said second position, a magnetic core within said coil, said core movable toward and away from said armature, and spring means coaxial with said coil for urging said armature to said first position.

2. A rely as defined by claim 1 further including means 5. for varying the force exerted by said spring means on said armature.

3. A relay comprising a coil of wire wound on a coil support, terminal means for said coil whereby said coil may be energized to produce a magnetic field, an armature normally spaced from said coil in position to be attracted by said magnetic field, an armature support forming part of the magnetic circuit for said magnetic field, and stationary hinge means connecting one end of said armature to said armature support, said hinge means providing a relatively loose hinge connection so that (1) when said coil is de-energized said one end of said armature can engage said armature support and (2) when said coil is energized said one end of said armature can move away from said armature support to establish a small gap therebetween which causes a change in the reluctance of said magnetic circuit.

4. A relay comprising an armature having a resilient contact member carried thereby but insulated therefrom, means hingedly supporting said armature for pivotal movement, first means positioned to be engaged by said contact member as said armature pivots in one direction and second means positioned to be engaged by said contact member as said armature pivots in the opposite direction, said first and second means determining first and second limits of travel respectively of said armature, said first means constituting an electrical contact, a coil of wire wound on a coil support, terminal means for said coil whereby said coil may be energized to produce a magnetic field, said coil disposed so that when it is energized the attractive force of its magnetic field will cause said armature to swing in said one direction to said first limit, and a spring urging said armature in said opposite direction and having a force suflicient to hold said armature at said second limit when said coil is deenergized, said contact member having just enough resiliency to allow small movement of said armature at said first limit without disengagement of said contact member from said first means.

5. A relay comprising a coil, terminal means for said coil whereby it may be energized to produce a magnetic field, an armature positioned to be attracted by said magnetic field, an armature support, means coacting with said armature and support to complete a magnetic circuit for said magnetic field, and stationary hinge means connecting one end of said armature to said armature support, said hinge means comprising a wire member anchored to said armature support and extending through said armature in a loose fit which permits lost motion between it and said one end so that said one end can directly engage said armature support and also can move away from said armature support to establish a small gap therebetween which causes a change in the reluctance of said circuit.

6. A relay comprising a coil wound on a 'hollow coil support, terminal means for said coil whereby said coil may be energized to produce a magnetic field, an armature in position to be attracted by said magnetic field, means pivotally supporting said armature for swinging movement toward said coil in response to said magnetic field, a hollow magnetic core within said hollow body, a spring within said core urging said armature away from said core, and means for varying the force exerted on said armature by said spring, said core moveable axially toward and away from said armature for varying the spacing between it and said armature.

7. A relay as defined by claim 6 further including a magnetic casing enclosing said coil support and coil, said casing forming part of the magnetic circuit of said coil, and further wherein said core member is screwed into an end wall of said casing and is moveable axially by rotation relative to said end wall.

8. A relay comprising a casing of magnetic material containing an electromagnet assembly and having a header assembly secured in one end thereof; said electromagnet assembly comprising a coil energizable to generate a magnetic field and a magnetic core within said coil; said header assembly comprising terminal means for energizing said coil, a magnetic ring secured to said casing, a magnetic armature support attached to said ring, an armature, and means hingedly connecting said armature to said armature support; the magnetic circuit for said field including said casing, core, ring, armature support and armature and being characterized by a primary air gap between said armature and core and a secondary air gap between said armature and support, said primary gap always present but having a predetermined minimum value when said coil is energized, and said secondary air gap having a predetermined maximum value when said coil is energized and a predetermined minimum value when said coil is de-energized.

9. A relay comprising an elongated casing, a hollow coil support disposed in said casing with its longitudinal axis parallel to the corresponding axis of said casing, a coil of wire wound on said coil support, said coil support including a magnetic core for said coil and also spring means, a header assembly secured in one end of said casing, said header assembly comprising an armature, means hingedly supporting said armature at one end for swinging movement of its other end toward and away from one end of said coil support, terminal means for energizing said coil to produce a magnetic field which attracts said armature, first and second stationary contacts spaced from said armature, and a third resilient contact attached to but insulated from said armature for engaging said first contact when said coil is de-energized and said second contact when said coil is energized, said armature free to move within limits determined by engagement of said third contact with said first and second contacts, said other end of said armature spaced from said core when at the limit determined by engagement of said third contact with said second contact, said spring means located within said coil support and disposed so as to bias said armature away from said coil support.

10. A relay as defined by claim 9, wherein said first and second contacts form part of said header assembly.

11. A relay comprising a casing formed of magnetic material, a magnetic assembly within said casing, and a header assembly attached to and mounted within one end of said casing; said magnetic assembly connected to said casing and comprising a bobbin having a hollow body, a core of magnetic material movably mounted within said hollow body, a coil wound on said bobbin, and terminals for said coil; said header assembly comprising a plurality of terminal leads, means for conductively connecting two of said leads to said terminals so that said coil may be energized from a source exterior of the header assembly, a first contact connected to another of said leads within said casing, an armature pivotally anchored at one end, a second contact attached to said armature in position to engage said first contact when said armature is caused to pivot by the magnetic field generated when said coil is energized, and means for conductively connecting said second contact to still another one of said leads so that an external circuit may be completed when said second contact engages said first contact; said casing, said core, and said armature forming part of the magnetic circuit for the flux of the field generated by said coil.

12. A relay as defined by claim 11 further including spring means within said core urging said armature in a direction to separate said first and second contacts.

13. A relay as defined by claim 12 further including means for varying the force exerted by said spring on said armature.

14. A relay comprising a casing, a coil assembly within said casing, and a header assembly attached to one end of said casing; said coil assembly attached to said casing and comprising a coil wound on a coil support having a pair or conductive segments at one end connected to the ends of said coil; said header assembly comprising switch means adapted to be actuated by the magnetic force of said coil when the latter is energized and a plurality of terminal leads for said coil and said switch means; and a pair of coil springs mounted on two of said leads, said springs engaging and axially compressed by said conductive segments so as to provide electrical connections between the ends of said coil and said two leads, said two leads bent within said casing to provide offset portions adapted to keep said springs axially compressed against said segments and make positive contact with said two leads at all times.

15. A relay comprising a casing, a coil assembly within said casing, and a header assembly attached to one end of said casing; said coil assembly attached to said casing and comprising a coil wound on a coil support having a pair of conductive segments at one end connected to the ends of said coil; said header assembly comprising switch means adapted to be actuated by the magnetic field generated'by said coil when the latter is energized and a plurality of terminal leads for said coil and said switch means; said magnetic field having a magnetic circuit which includes said casing and a part of said header assembly; and a pair of coil springs mounted on two of said leads, said springs engaging and axially compressed by said conductive segments whereby to provide electrical connections between the ends of said coil and said two leads.

References Cited by the Examiner UNITED STATES PATENTS 2,009,892 7/ Leece 20087 2,347,735 5/44 Coyne 200166 2,444,198 6/48 Hasselhorn 317 2,467,063 4/49 Walton 2001 11 2,547,131 4/51 Lewus 317198 2,623,136 12/52 Mekelburg et a1 200--87 2,777,923 1/57 Munson et al 317-198 2,860,204 11/58 Hughes et al 317-198 X 2,892,058 6/59 Tancred 317198 2,945,930 7/60 Priesemuth 20087 3,048,749 8/62 Koehler ZOO-87 3,051,804 8/62 Mayer 200104 3,061,765 10/62 Hess 317-198 3,076,073 1/ 63 Townsend 20087 3,092,701 6/ 63 Sikorski 20087 BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

9. A REALY COMPRISING AN ELONGATED CASING, A HOLLOW COIL SUPPORT DISPOSED IN SAID CASING WITH ITS LONGITUDINAL ASIX PARALLEL TO THE CORRESPONDING AXIS OF SAID CASING, A COIL OF WIRE WOUND ON SAID COIL SUPPORT, SAID COIL SUPPORT INCLUDING A MAGNETIC CORE FOR SAID COIL AND ALSO SPRING MEANS, A HEADER ASSEMBLY SECURED IN ONE END OF SAID CASING, SAID HEADER ASSEMBLY COMPRISING AN ARMATURE, MEANS HINGEDLY SUPPORTING SAID ARMATURE AT ONE END FOR SWINGING MOVEMENT OF ITS OTHER END TOWARD AND AWAY FROM ONE END OF SAID COIL SUPPORT, TERMINAL MEANS FOR ENERGIZING SAID COIL TO PRODUCE A MAGNETIC FIELD WHICH ATTRACTS SAID ARMATURE, FIRST AND SECOND STATIONARY CONTACTS SPACED FROM SAID ARMATURE, AND A THIRD RESILIENT CONTACT ATTACHED TO BUT INSULATED FROM SAID ARMATURE FOR ENGAGING SAID FIRST CONTACT WHEN SAID COIL IS DE-ENERGIZED AND SAID SECOND CONTACT WHEN SAID COIL IS ENERGIZED, SAID ARMATURE FREE TO MOVE WITHIN LIMITS DETERMINED BY ENGAGEMENT OF SAID THIRD CONTACT WITH SAID FIRST AND SECOND CONTACTS, SAID OTHER END OF SAID ARMATURE SPACED FROM SAID CORE WHEN AT THE LIMIT DETERMINED BY ENGAGEMENT OF SAID THIRD CONTACT WITH SAID SECOND CONTACT, SAID SPRING MEANS LOCATED WITHIN SAID COIL SUPPORT AND DISPOSED SO AS TO BIAS SAID ARMATURE AWAY FROM SAID COIL SUPPORT. 